What investors should learn about chasing hot markets.

Tech stocks aren't sunk. But the ship has sprung a leak. Should you bail out?

After climbing 244% from its 2009 low through March 5, the Nasdaq Composite Index has dropped 8.2%, tumbling 3.1% on Thursday alone—its biggest one-day drop since November 2011. Certain slices of the tech market look more perilous.